The overall aim of this project is to determine whether and why the Affordable Care Act's (ACA) menu labeling requirement impacts obesity by examining changes in consumer behavior and restaurant menus. Due to the relationship between eating outside of the home and obesity and the difficulty of consumers in accurately determining the nutritional content of menu items, the ACA requires chain restaurants to post calorie information on menus. This requirement will be implemented on December 1, 2015 and builds upon similar state and local laws first implemented in 2008. Preliminary evidence suggests that changes in body mass index (BMI) over time in counties that previously introduced a menu labeling requirement fell in recent years relative to nearby counties. In contrast, prior research on local menu labeling laws primarily examines changes in items ordered at large chain restaurants and generally finds small or no changes in the amount of calories purchased after calorie counts are posted on menus. Such a narrow focus misses numerous other potential changes in restaurant menus and consumer behavior due to these requirements. This project significantly expands on the prior literature by examining the nationwide implementation of the ACA's menu labeling requirement and examining the broader impacts of this requirement on behavior. Specifically, this project will evaluate the impact of the ACA's menu labeling requirement on (1) restaurant menu offerings and prices, (2) consumer eating habits, (3) physical activity, and (4) body mass index and obesity. Difference-in-differences comparisons over time before and after the implementation of the menu labeling requirement among groups affected by the requirement and groups not affected will provide estimates of the impact of menu labeling. Affected restaurants are chains with 20 or more locations that did not voluntarily previously post calories on menus and are located in areas without a prior local mandate. Affected consumers are individuals living in counties or states without a pre-ACA calorie posting mandate. To construct these estimates, this project will involve collecting and analyzing menus and nutritional content from chain restaurants, surveying consumers in areas with prior calories posting mandates and surrounding regions and analyzing the resulting data, and analyzing data from the Behavioral Risk Factor Surveillance System (BRFSS). The expected outcomes of this project are an understanding of the impact of greater access to information in the form of calorie posting requirements on obesity and the mechanisms through which calorie posting influences obesity. Thus, this project will inform policymakers and researchers about whether and how the calorie posting mandate in the Affordable Care Act impacts obesity rates.